Abstract

The comprehension of the real behaviour of pile foundations under earthquake loading is very important, since it can significantly affect the performance of the superstructure. As a matter of fact the experience of recent earthquake has confirmed that piles can suffer extreme damage and failure under earthquake loading. The case histories from Kobe earthquake (1995) indicate that not only the inertial actions but also the kinematic ones, due to ground movements, which was overlooked in design specifications at that time, had significant effects on pile damage. The purpose of this work is to examine the complex soil-structure interaction problem, on the basis of the results of an original experimental activity on shaking table, particularly devoted to the evaluation of kinematic interaction effects in layered soil configurations. A great amount of data has been collected during the experimental study, relative to around 400 shaking events on a single pile. The test focused on three different subsoil configurations, a monolayer and two layered deposits, with the aim of highlighting the influence of soil stiffness contrast on kinematic interaction. The effects of different pile head conditions, including the presence a single degree of freedom superstructure, have been investigated. The pile response has been evaluated mainly in terms of bending moments induced by both kinematic interaction and coupled kinematic and inertial effects. The seismic motions at the foundation level, due to kinematic interaction, has been investigated and compared with the free field response.